Genomic analysis of Plasmodium azurophilum in eastern Caribbean Anolis lizards
The malaria parasite Plasmodium azurophilum lives in both vertebral an d insect hosts. The vertebral hosts are the Anolis lizards 1. Prior to a study by Susan L. Pe rkins (2000) it was believed that the '' P. azurophilum f''ound in the erythrocytes and leukocytes o f Anolis lizards were the same species. However, after analyzing the mitochondrial cytochrome b gene sequencing of the P. azurophilum ''she discovered there were two genetically distinct lineages of the parasite, one infects the erythrocytes and the other infects the leukoc''ytes of the Anolis lizards. Th''e parasites have identical morphology under a microscope however are isolated reproductively from each other and have evolved independently from each other 2. Methods Perkins S.L. (2000) collected ''Anolis lizards from eight islands around the eastern Caribbean. She did this by hand or slip noose catch and used a toe clip to obtain blood for DNA extraction. For each of the eight islands three parasites that infected the erythrocytes and three parasites that infected the leukocytes were collected. A fragment of the mitochondria cytochrome b gene was amplified using DW1 and DW3 primers for high infections, and DW2 and DW4 primers for weak infections 2. A total of 554 base pairs of the mitochondria cytochrome b gene were used for the analysis. The outgroup used in the phylogenetic analysis were the Plasmodium gallinaceum. To construct the phylogenetic tree she used neighbor joining, unweighted maximum parsimony, and maximum likelihood 2. Discussion In the past parasitologists have identified different malaria parasites based on morphological traits like number of merozoites per schizont, the shape of the gametocytes, the species of host infected, and the symptoms of the host infected. This however can be unreliable because the morphology and life history of the malaria parasite can vary in each of its hosts. Even for the P. azurophilum the erythrocytes and leukocytes of the host look identical and only differ slightly in size. The only phenotypic trait that separates the parasites are the host cells by which they infect. This study found that the'' P. azurophilum'' that reside in the erythrocyte differs from the P. azurophilum that resides in the leukocyte by 3.1%, which is comparable to the difference between other species of Plasmodium. She also found that there are no shared haplotypes between parasites that are in erythrocytes and leukocytes. It seems like the two species of P. azurophilum can coexist in the same host however they are reproductively isolated from each other. In this study Susan Perkins (2000) demonstrates that the molecular phylogeny of the P. azurophilum has two evolutionary lineages, and colonized the island independently of each other because they are not close relatives 2. The phylogenetic tree composed by Susan Perkins uses a bootstrapping method. Bootstrapping is a way to asses the quality of sequence-based phylogenies. It is done by creating new alignments by randomly picking a new alignment from the original alignment. A new phylogenetic tree is reconstructed with each new alignment. After that a consensus tree is formed, which summarizes all the tree replicated made from the alignments. A confidence value for an edge is place in the tree to define the number of replicates that appeared. If the confidence value is above 75% it is considered correct 3. References 1. Wikipedia, Plasmodium azurophilum (2013) Link: http://en.wikipedia.org/wiki/Plasmodium_azurophilum 2. Perkins S.L. "Species concepts and malaria parasites: detecting a cryptic species of Plasmodium." Proc. R. Soc. Lond. B 22 November 2000: 2345-2350. Link: http://rspb.royalsocietypublishing.org/content/267/1459/2345.full.pdf 3. Shi J., Zhang Y., Luo H., Tang J. (2010) Using jackknife to assess the quality of gene order phylogenies. BMC Bioinformatics. 11:168. Link : http://www.biomedcentral.com/1471-2105/11/168